Field of the Invention
Portable computer is the main tool in the information age. The space, weight and anti-vibration of the portable disk drive are the key issues in the portable computer design. However, in today design, the CD player, magnetic disk drive, floppy disk drive, optical disk drive are the separate designs. It is impossible to incorporate all the four kinds of disk drives in a portable computer. In the portable environment, the space is limited to one mini-disk. The mini-disk needs to have the ultra high density to store a large amount of data. We need to design a new approaches to push for the extreme limit of the ultra high density.
Furthermore, the portable computer is operated in the highly vibrant environments such as joggling, running, etc. The portable computer needs to continue playing without the interrupt due to the failure of the tracking of the head. For the above reasons, a completely revolutional new invention of disk drive is invented. We use the coordinate/clock track to reduce the access time and increase the high density. We use the universal head to reduce four different disk drives to be one single disk drive. We use the laser pin to decouple the tracking problem to be two sub-problems to have the capability to track the head directly push the extreme high density for the mini-portable disk. The concept of the trainee actuator follows and traces the trainer actuator with the guidance of the laser pin is a complete new concept. In our patent, we apply the angular amplification of the laser beam to the diffracted grating for the trainee actuator and use the laser guiding pin to guide the trainee actuator. The trainee actuator rotates to follow the guidance of the laser guiding pin.
As shown in the U.S. Pat. No. 5,268,801, the Hazel's patent uses a mirror attaching to the rotational axle of the trainee actuator. It will takes a lot effort to align the mirror on the trainee actuator accurately. Furthermore, his patent has the "angular amplification factor" of the laser light. However, the deflected light passing through the window at an angle. It will induce the track density uniformity errors which are not endurable in the portable mini-disk. It will reduce the track density a lot. Under the same set up of the servo system, even a small deviation angle of the mirror will cause the disk to lose a lot tracks or to start to write on the track which is outside the valid region. The horizontal swing of the setup table (mechanical translator 42) is so large. The mechanical translator mechanism will be worn out pretty soon. It is impossible to get the accurate alignment. The measurement facilities are at the far end to swing back and forth to search the tiny weak laser light. For the swinging long table, the small mechanical vibration will disturb the optical setup a lot.
As shown in the U.S. Pat. No. 5,268,801 Hazel At Al's principle is based on sensing the angle of the reflection laser beam. His principle, sensing the angle of the reflection beam, force him to place his position interpreter in the surface being parallel to the rotating axis of the actuator. This is not desirable location because it is not similar or near the location of the magnetic heads. Because the angle of the reflection beam is always parallel to the rotating axis of the actuator, hence his technique is inoperative in the most preferred situation in which the plane containing the position interpreter (the mirror for Hazel's principle) is perpendicular to rotating axis of the actuator. Moreover, Hazel at al's technique must use the arc transparent window which is too expensive to be use in the magnetic disk drive.
In the U.S. Pat. No. 5,325,349, the Taniguchi's patent uses an diffraction grating mounted on the actuator of the disk drive having the fixed laser source. Taniguchi's technique is well known by those skilled in the art to use moving diffraction grating and a fixed laser source to determine the position of the subject of interest. To meet the form factor of the magnetic disk drive industry, an angular actuator must be utilized. The angular diffraction grating is a diffraction grating with a plurality of lands and grooves being intercepted at one point and the linear diffraction grating is a diffraction grating with a plurality of lands and grooves being parallel. Hence Taniguchi must use an angular diffraction grating in his patent because the laser source of his design is fixed. To utilize the angular diffraction grating, one must align the virtual rotating point (as shown in FIG. 3 in Taniguchi's patent) of the angular diffraction grating with the rotating axis (as shown in FIG. 2 in Taniguchi's patent) of the magnetic disk drive actuator. This virtual rotating point is not physically real. It is an imaginary interception point of all the extended lands and grooves of the angular diffraction grating. Hence it is require the complex tool and highly skillful technician to assembly the angular diffraction grating. Beside those problems above, as he stated in his patent specifications, Taniguchi At Al must degrade the position resolution to trade off for the use of a smaller angular diffraction grating. Moreover, Taniguchi At Al's technique is the laser source fixed (not moveable); therefore the technique must sense different lands and grooves of the angular diffraction grating to cover the whole angle of rotation. None of angular diffraction grating is perfect and hence there are mismatched lands and grooves. Beside of these differences of lands and grooves there is distortion of the angular diffraction grating. It is impossible to manufacture the high volume magnetic disk drive with the utility of an angular diffraction grating in every magnetic disk drive.
In Taniguchi's patent, there is no "angular amplification factor" of the laser beam. Even the laser light is raised up to have the longer laser light flying path, the accuracy of the track position doesn't improve at all. On the contrary, the accuracy of the track position is decreased.
Increasing the laser light flying path, only there is the angular change of the laser beam, the resolution of the track density can be increased. The actuator is followed the sinusoidal curve to find the track position. At the track position, the sinusoidal curve has the differential to be zero and follow the variance to be the cosine. In other words, it is not sensitive for the variance of the track position. To get high accuracy of the track, we need to increase the sensitivity of the diffraction grating. Both of their patents use the external reflective means attaching to the magnetic disk actuator arm. It has the reproduction problem in the mass production line. However, it is noted that the Hazel's patent cannot apply to the Taniguchi's patent. The Hazel's patent has only the angular amplification concept; the Taniguchi's patent has only the diffraction grating concept. For the Taniguchi's patent, it is no use to increase the flight path. Taniguchi's patent has no angular amplification factor at all. It is impossible to combine the patent having no angular amplification with the patent having the angular amplification factor. In Taniguchi's patent, for the laser beam having no angular change, increasing the laser traveling path, the larger the beam spot is and the lower the resolution of track density is.
Without our new concept of the trainee actuator tracing the laser guiding pin to divide and conquer the problem, the angular amplification of the laser beam cannot cooperate with the diffraction grating. Using the new concept, trainee actuator tracing trainer actuator with optical pin, the problem is divided to be angular amplification and the exact tracking problems.
As shown in FIG. 4B, the prior arts of their patents do not know how to use the divide conquer methodology. Both of them try to locate the actuator track position directly. Their patent have no servo arm concept and exact tracking concept. So they cannot divide and conquer the problem. It is noted that Taniguchi's patent doesn't have the servo writer trainer actuator concept.
As shown in FIG. 4C, our patent combines the trainer actuator concept with laser pin concept, using the divide and conquer methodology, our solution is a two-steps solution. The trainer actuator is to divide the track problem to be the first sub-problem: track position of the servo actuator; and the second sub-problem: the tracking problem of the trainee actuator. We first set the track position of trainer actuator with high accuracy, then we set the actuator to follow the servo arm exactly. The track position sub-problem of the trainer actuator is solved with the combination of angular amplification and the reflective diffraction. The trainee actuator tracking sub-problem is solved with the laser pin.
For the angular amplification of the laser beam, instead of swinging the "translator setup table" as the Hazel's patent does, in our patent, we swing the laser beam to have the "angular amplification". The translator setup table for Hazel's table has the limit of the table length. Our patent has no limit on the length of the laser path.
Because magnetic disk drive industry is very competitive, the most important fact is to maintain the minimum cost. To achieve this objective, to put the expensive component (the angular diffraction grating) on the equipment (servo writer system) of the manufacture, not on the final product (the magnetic disk drive). The customer will not buy it. Furthermore, it causes the alignment problem and the reproduction problem.
Furthermore, for the ultra density disk drive, "as it is" is the most robust design principle for the portable mini-disk drive. Otherwise, the track position works can not repeat at all. The minor deviation in the alignment of the human installed the mirror or diffraction grating in Hazel's or Taniguchi's patents will cause the deviation of several hundred track errors in the ultra high density disk. In other words, the different disks have the several hundreds tracks mismatch in the track position process. This mismatch result cannot be endured. So, both the Hazel's patent and the Taniguchi's patent are not workable patent.
In the high tech field, minor violation of the fundamental principle will cause the design not working. Both the Hazel's patent and Taniguchi's patent violate the fundamental of magnetic disk drive principle, as it is. They added the extra components to the disk drive. So their disk drive doesn't work in the mass production. It is impossible to re-produce the same alignment and track position result for the different disk. Our patent follows the fundamental principle of "as it is". Our disk drive system not only works but also save a lot cost of the disk drive. For the portable mini-disk drive, it should not add any additional component in the servo writing process.
The Taniguchi's patent needs to install the high cost angular diffraction grating on the actuator. With the same setup, the Hazel's patent has to install the mirror with high accuracy to have the trainee actuator to locate at the proper track region. Otherwise, the Hazel's patent has to re-calibrate the setup for each disk drive to locate the actuator in the correct track region. This work cannot be repeated exactly for each disk drive that each disk drive has the different track region. This cannot be accepted for the mass production. Basically, the Hazel's patent is useless at all. The same reason is applied to the Taniguchi's patent. It is impossible to install the diffraction grating on the actuator exactly at the same position. However, the track region is defined by the position of the diffraction grating. So, no two disk will have the same track reason. For the ultra high density, such kind a manual error of alignment causes hundred tracks difference. Such kind a result cannot be accepted.
Comparing with the Taniguchi's and Hazel's patents, our invention is the only useful and practical system. For our patent, the position device such as diffraction grating is mounted on the servo writer system instead of the disk drive system. The trainee actuator has both the head and the rotational axle to be aligned with the virtual head and rotational axle trainer actuator respectfully. For the same servo writer, all the disk drive have the same track regions. It is easily to calibrate the different servo with the same standard. So, all the disk drive of our patent have exactly the same track region definition. It is pretty easy to standardize the universal disk in the mass production.
As bit density (bits per inch) increases, the read and write channel must reliably record and retrieve serial data. To retrieve the recorded data, the control unit must have two signal lines: a data signal and a sampling clock. Conventional read channel receives only one data signal from a subject magnetic head. They must extract the sampling clock signal by means of a phase lock loop. The read channel of conventional magnetic disk drive can not utilize a crystal system clock as a reference because of the following factors:
a) The static and dynamic speed variation of spindle motor; PA1 b) The eccentricity generated during fastening disks to the shaft of the magnetic disk drive spindle motor (This eccentricity creates variation in the relative linear velocity between the magnetic heads and disks); PA1 c) The run-out of Spindle motor.
The synchronization of all of the previously designed magnetic disk drives using the crystal system clocks is not optional. The closed loop speed control system in the prior art utilize back electromotive-force or Hall-effect sensors to regulate the velocity of the spindle motor. Hall-effect sensors are very fragile. They can be destroyed during the component assembly of the spindle motor. Furthermore, there are very few pulses per revolution generated by these sensors. Hence, the resolution is too coarse to have precise synchronization between the spindle motor and a crystal reference system clock. These systems also require a component actively trimming process to obtain a good average speed (not an instantaneous speed). The component actively trimming process is very expensive and it is labor intensive.
Conventional read channels (both analog and digital read channels) lose their synchronization when encountering a media defect or a drop out. They require more intelligent circuits to detect a media defect and to inhibit phase detector output. Currently, the conventional read channels cannot match the increasing rate of bit density. The speed of the spindle motor in the magnetic disk drive must therefore be decreased. This low spindle motor speed increases the access time of the magnetic disk drive.
It is very expensive to design and fabricate the high capacity and performance magnetic disk drive using the conventional designs. It requires high precision components to compensate for the weak interconnection of the head disk assembly subsystems. Therefore, both a high track density and a high bit density demand a new concept of design and manufacture.
Unlike the previously designed magnetic disk drives, the universal disk drive subsystems of this invention are strongly interrelated. A chief aspect of the intimate interconnection is a precise synchronization between the spindle motor and the crystal system clock. The read and write channels and the read back servo position signals can take advantage of this precise synchronization for improving performance and reliability.